About Sleep Calculator

Sleep Calculator is a free online tool that answers every version of the sleep question — the best time to go to bed for your wake-up time, the best time to wake up if you sleep now, and exactly how long you slept between any bedtime and wake-up time. It was made by Anees Ur Rehman for everyone who is tired of waking up groggy: the trick is not just sleeping longer, it is waking up at the end of a 90-minute sleep cycle.

Every answer is worked out exactly from 90-minute sleep cycles, and shows how it was calculated so you can check it yourself — for example, to wake at 7:00 AM, the best bedtimes are 10:00 PM (6 cycles, 9 hours), 11:30 PM (5 cycles, 7.5 hours), 1:00 AM (4 cycles, 6 hours) and 2:30 AM (3 cycles, 4.5 hours). The 7.5-hour and 9-hour options are the ones most adults should aim for. The wake-up calculator allows about 15 minutes to fall asleep, because that is how long most people take.

Sleep Calculator is free forever. There is no account, no sign-up, no install and no limit. Your times are calculated in your browser and never sent to any server. The site is supported by advertising (Google AdSense) — the ads keep the tool free, and you can choose personalised or non-personalised ads with the cookie banner at the bottom of the page.

An honest note about sleep cycles

Sleep cycles average about 90 minutes and vary from person to person, and they change through the night — so every result here is an estimate, not medical advice. If you snore loudly, stop breathing in your sleep, feel tired all day despite sleeping enough, or cannot sleep for weeks, please see a doctor. A real sleep problem needs real medical help, not a calculator.

Who made Sleep Calculator?

Sleep Calculator is made by Anees Ur Rehman, who also runs ToolKamai (free online tools), AI Creator Studio (free AI tools), Percentage Calculator, Discount Calculator and PDF Tools. If a calculation looks wrong, or you want another calculator added, please contact us — every message is read.